Require a valid bearer token (not just loopback peer IP) for settings WRITE endpoints (/settings/llm, /settings/data-sources) when API_AUTH_KEY is configured, closing a DNS-rebinding / loopback-trust bypass while keeping zero-config local dev writes.
Also reconciles the DNS-rebound security tests across the #241-#245 sprint: now that #242's rebound-host middleware 403s loopback requests with an attacker-controlled Host before they reach the route, the end-to-end rebound tests for /swarm/runs and /sessions/messages (#243) and /settings/llm (#245) assert the request is rejected at the host-gate layer (403) and never reaches the shell-tool / settings-write decision. Full suite: 3217 passed.
